Bartz v Anthropic is some good authority on fair use (https://storage.courtlistener.com/recap/gov.uscourts.cand.43...). Still, it can't be said to be definitive because the plaintiff's arguments on market harm (with respect to fair use, not piracy) were limited and there were, as far as I can remember, no compelling examples provided of model output reproducing large swathes of training text.